The present invention relates to winning machines for winning coal, minerals, and the like.
More particularly, the present invention is concerned with a rotating head for such a winning machine.
It is known in the prior art to provide a power loader which has a cutting tool such as a rotating head (usually a drum or drums) armed with picks or some form of cutter bits. Such a rotating head includes a tubular support and one or more blades which may extend helically about the circumference of the tubular support. The blades are rigidly connected (e.g., welded) to the outer surface of the support. A plurality of cutting units are mounted equally spaced on the blades. Each of the cutting units includes a pick holder rigidly connected (e.g. welded) to the blade and a pick detachably fixed in the holder. Cutting is achieved by the picks which extend from the periphery of the blades towards a working (i.e., mining) face of the material to be mined. The tubular support has one open end which faces the working face and which is closed by an end face plate.
It has been also suggested to provide the rotating head with a conical locking ring which is welded to the end face plate and extends outwardly away therefrom towards the working face. The outer periphery of the locking ring may also be provided with a plurality of the cutting units similar to those provided on the blades. The picks, which are fixed in the corresponding holders welded to the outer periphery of the locking ring, extend towards the working face. Due to the conical locking ring the contact of the end face of the rotating head with the working face is considerably reduced as opposed to a rotating head having the end face entirely planar. Obviously, the forces of the engagement between the end face of the rotating head and the working face and the frictional losses in such an engagement are considerably reduced in the case of the rotating head having the conical locking ring. Accordingly, the effectiveness of the cutting process is increased, whereas the dust development during the cutting process is reduced.
It has been recognized, that any inclination of the end face of the rotating head from the planar configuration leads to improving of the cutting process. It is further advantageous to maintain a cone angle of the end face, that is an angle between any imaginable line extending radially along the end face and the axis of the rotating head, substantially below 90.degree.. In practice, the cone angle is between 30.degree. and 85.degree.; however, a preferable range of inclination would be between 50.degree. and 70.degree. . Quite sufficient results have been obtained with the cone angle of 60.degree..
It is very difficult and time consuming to displace such a rotating head in the mine. However, it is often necessary to remove the head from the mine to the ground surface, for example, for repairing purposes.
However, such displacement is not always possible or very easy to accomplish, for example, due to the unpredictable and, therefore, uncontrollable swelling of the floor of the mine which leads to narrowing of the main passage of the mine. Thus, in order to remove the head from the mine, it becomes necessary to excavate additional material from the mine only to widen the main passage. Obviously, any additional excavation is relatively complicated and expensive. Thus, the cutting (i.e. mining) process, which is quite expensive by itself, becomes even more expensive due to the above-mentioned additional excavations.
The blades on the tubular support have the same outer diameter, so that the picks which are mounted on the blades constitute a common generatrix. Therefore, the spaces defined by the corresponding surfaces of the blades on the one hand and the respective portions of the outer surface of the tubular support on the other hand are equal to one another. This leads to the fact that the removed material moves along a relatively wide section all the way until it reaches a conveyor which results in an undesired comminuting of the removed material into small particles. Besides, since the removed material moves always along the passage of the same cross-section there might be a situtation where the removed material develops a plug in this passage, which plug unavoidably results in negative consequences for the whole power loader.
In German Offenlegungsschrift No. 2647171 it has been suggested to provide the tubular support with a conical linear outer surface having a first end which faces the working surface and an axially spaced second end which faces away from the working face of the mine. In this case, the first end has the largest outer diameter, whereas the second end has the smallest outer diameter. Thus, the passage for the removed material at the first end of the tubular support is smaller than that at the second end of the support. Advantageously, the transporting of the removed material in direction from the first end, that is from the working face, towards the second end of the tubular support and onto the conveyor located adjacent to the second end of the tubular support is considerably facilitated due to the cone angle of the outer surface of the support.
However, it has been recognized, that the linear extension of the outer surface of the tubular support is not always satisfactory with respect to the requirements made to a reliable, simple and fast transporting of the removed material from the working surface towards the conveyor. In fact, the linear increase of the cross-section of the passage for the removed material has been found to be the reason of the unsatisfactory conditions during transporting of the removed material from the working face.
The rotating head in accordance with the German Offenlegungsschrift No. 2647171 consists of two halves which may be connected to each other right in front of the working face. Obviously, this fact considerably facilitates the displacement of the head itself. Especially, the displacement of the head back onto the ground surface becomes considerably less complicated.
However, in order to repair such a head, the latter still has to be moved from the mine onto the ground surface. Such a displacement of the head causes significant expenses comparing with an initial purchase-cost of the head. Thus, for example, the repair- and displacement expenses may sometimes exceed the purchase-cost of a new head. Nevertheless, it has never been suggested, even in the case of the one-piece head, to provide such a rotary head that can be assembled underground and left there, for example, after being broken.
The assembling of the rotating head in accordance with the above-mentioned German Offenlegungsschrift No. 2647171 is very complicated. The tubular-support halves are connected to each other by screws which after a relatively short time of use corrode significantly due to the direct contact with underground water. Thus, the corroded screws can be moved (i.e. unscrewed) only upon applying thereto a significant pulling force (i.e. torque) which is a quite difficult task to accomplish, especially if considered the limited free space in the mine.
Moreover, the separate conical locking ring additionally increases the cost of the rotating head, since the ring has to be connected to the conical tubular support. Obviously, additional operations of making (or purchasing) the locking ring and welding this ring onto the support correspondingly increase the overall cost of the rotating head.